linux-kernel - [PATCH 4.4 05/23] fuse: initialize the flock flag in fuse

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Message-Id: <20170815011754.449769838@linuxfoundation.org>
Date:   Mon, 14 Aug 2017 18:18:22 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mateusz Jurczyk <mjurczyk@...gle.com>,
        Miklos Szeredi <mszeredi@...hat.com>
Subject: [PATCH 4.4 05/23] fuse: initialize the flock flag in fuse_file on allocation

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mateusz Jurczyk <mjurczyk@...gle.com>

commit 68227c03cba84a24faf8a7277d2b1a03c8959c2c upstream.

Before the patch, the flock flag could remain uninitialized for the
lifespan of the fuse_file allocation. Unless set to true in
fuse_file_flock(), it would remain in an indeterminate state until read in
an if statement in fuse_release_common(). This could consequently lead to
taking an unexpected branch in the code.

The bug was discovered by a runtime instrumentation designed to detect use
of uninitialized memory in the kernel.

Signed-off-by: Mateusz Jurczyk <mjurczyk@...gle.com>
Fixes: 37fb3a30b462 ("fuse: fix flock")
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/fuse/file.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -46,7 +46,7 @@ struct fuse_file *fuse_file_alloc(struct
 {
 	struct fuse_file *ff;

-	ff = kmalloc(sizeof(struct fuse_file), GFP_KERNEL);
+	ff = kzalloc(sizeof(struct fuse_file), GFP_KERNEL);
 	if (unlikely(!ff))
 		return NULL;